1. Field of the Invention
The present invention relates to a method for analyzing parameters during the production of wafers, and more specifically, to a method of analyzing wafer test parameters.
2. Description of the Prior Art
In the semiconductor industry, numerous manufacturing processes, such as lithography, etching, an ion implantation processes, are necessarily performed by utilizing different semiconductor machines to produce semiconductor products. It is therefore a major task to improve the production efficiency and the performance of the product by regularizing daily operation, increasing production yield, detecting and eliminating defects during manufacturing, and periodically maintaining facilities for production, so as to meet the requirements of customers. Generally, defects during manufacturing can be detected by analyzing parameters of in-line quality control (in-line QC) items, defect inspection items, sample test items, wafer test items and final test items. Among these parameters, the wafer test parameters are obtained by performing a pause refresh test, a function test or a power supply current test (IDDQ test).
Please refer to FIG. 1 and FIG. 2, which respectively represent a flow diagram of method of inspecting lots of wafers 20 and a schematic top view of a wafer 20 with defects according to the prior art. As shown in FIG. 1 and FIG. 2, the wafer 20 with defects are divide into multiple of dies and comprises a plurality of defective dies 21 and a plurality of non-defective dies 22, which are respectively represented by black and white blocks in FIG. 2.
At the beginning of the method, a step 101 is utilized by an inspector to perform wafer test items, comprising the pause refresh test, function test and power supply current test, on lots of wafers 20. A step 102 is then utilized to find out the wafers 20 with failed results. Thereafter, the inspector performs a step 103 to determine manufacturing processes, such as the lithography, etching and ion implantation process, and corresponding machines that cause failed results on the selected wafers 20 according to the distribution of the defective dies on each selected wafers and his/her experiences.
Finally, the inspector performs a step 104 to inspect and maintain those manufacturing machines determined in the step 103 so as to eliminate defects in production of subsequent lots of wafers 20.
However, since the inspector analyzes the distribution of the defective dies 21 to determine the abnormal manufacturing machines and process steps in the step 103 by his/her personal experiences, the accuracy of the analyzing results is not reliable. Therefore, engineers on the production line cannot immediately determine abnormal machines and process steps in a systematical manner as defects occur during manufacturing. As a result, the manufacturing efficiency is reduced, and the production cost is increased as well.